1. Field of the Invention
The invention relates to the field of measuring the diagnostics of automobiles, specifically the measurement of disc brake pads.
2. Description of the Prior Art
Traditionally, when the thickness of the lining material on disc brake pads is measured, the entire wheel must be removed from the vehicle. Once the wheel has been physically removed, a thickness or feeler gauge is selected from a collection of thickness gauges that range over ten to twelve different sizes. The selected gauge is then inserted down through the center of the caliper between the backing plate of the brake pad and the machined surface of the rotor. This traditional method of measuring brake pad thickness can take 5-15 minutes per wheel and can be quite physically demanding due to the size and weight of the tires of many current vehicles. Brake inspections have become routine in many high-end service centers, adding to costs and time to service the vehicles.
What is needed is a measuring device to quickly and accurately measure a small distance within a tight area such as in the wheel well of a vehicle without the necessity of taking off the wheel.
Several examples found in the prior art have attempted to solve this problem in one way or another, but unfortunately they also contain several limitations and drawbacks that make them unsuitable or undesirable for the purpose of the current invention. For example, many devices found in the prior art are capable of measuring very small gaps or slots. However, most of these prior art devices are placed at one edge of a gap to be measured and are then manipulated by the user to extend the distal tip or an inner rod until it telescopes to the other end of the gap. Once the distal end has reached the far side of the area to be measured, the user must then tighten or lock down the measuring portion of the device so that a measurement may be read from the device. These devices are also often bulky, clumsy and difficult to operate as they sometimes require two manipulations to get an effective and accurate reading. Additionally, some of these devices are too big to manipulated in small areas such as the space behind or through a wheel opening and therefore still require the wheel to be removed each time the brake pads are measured.
Other prior art devices for measuring small gaps, specifically those between the rotor surface and the backing plate of the brake pad, involve the use of a device which is permanently and physically coupled to the vehicle. This solution is extremely limited and usually used only on large trucks and other specially designed vehicles that have the necessary interior space available to accommodate such an option. Most passenger vehicles on the road today would not therefore be able to accommodate such a device.
What is needed is a brake pad measuring tool that is small, compact, quick, and easy to use and if possible, does not require the removal of any wheels from the vehicle and does not require permanent coupling to the vehicle.